Everything You Need to Know About Numbers in AP Style

The AP Stylebook is a popular style guide in the business and journalism worlds. But how should you write numbers in AP style? In this post, we explain everything you need to know, including:

• The general principles to follow for numbers in AP style.
• When to use numerals and when to spell out numbers as words.
• How to write very large numbers.
• When you should use Roman numerals rather than Arabic numerals.

For information on all the above, check out our guide below.

Numbers in AP Style

Produced by the Associated Press, the AP Stylebook has a few basic recommendations for how to write numbers. In general, you should:

• Spell out numbers up to nine (e.g., She spent four weeks in prison).
• Use numerals for ten and above (e.g., There were 112 stick insects).

These rules apply to both cardinal and ordinal numbers. However, the AP Stylebook also has guidance on when to use numerals and words for numbers in particular situations. And in these cases, you should stick to the specific advice regardless of how big or small the number is.

When to Use Numerals in AP Style

Key cases in which AP style suggests using numerals include:

• Academic course numbers (e.g., Philosophy 101).
• Addresses (e.g., 10 Downing Street).
• Ages (e.g., A 7-year-old boy, The tree is 200 years old).
• Dates, years and decades (e.g., Feb. 12, 2020, 1970s).
• Decimals, percentages and fractions (e.g., 5.6, 8%, 3 ½), except for simple fractions under one (e.g., two-fifths, three-quarters).
• Mathematics (e.g., 2 + 2 = 5, Multiply by 7 and add 3).
• Measurements (e.g., 4 miles, 5 ml) and money (e.g., $8, £100).
• Odds and ratios (e.g., A 2-1 chance).
• Page numbers and sequential designations (e.g., Page 34, Chapter 2).
• Recipes (e.g., 2 tablespoons of sugar, 1 cup of milk).
• Split decisions and votes (e.g., A 4-5 decision).
• Sport scores (e.g., The team won 6-0 in the replay).
• Times of day (e.g., 3:30 p.m., 6 a.m.), except noon and midnight.
• Vehicle names (e.g., Apollo 11, B-2 bomber), except for Air Force One.

The AP also suggests using numerals in tabular material, statistics, and sequences, even for numbers below ten.

When to Spell Out Numbers in AP Style

There are also a few times when you should always spell out a number:

• At the start of a sentence (e.g., Two thousand people attended), except for years (e.g., 2016 raised a lot of questions about democracy).
• In figures of speech (e.g., You’re one in a million), proper names (e.g., The Fab Four), and other customary usages (e.g., The Twelve Apostles).
• In casual or indefinite uses (e.g., Dealing with it one day at a time).

Except in the noted exception of years, these override the general rules for numeral use, so make sure to use words even for numbers over nine.

Millions, Billions and Trillions

For large round numbers, AP style suggests a mix of numerals and words:

Up to 5 million people may be affected.

It landed the company with a $2 billion lawsuit.

This provides a balance between simplicity and clarity.

Roman Numerals in AP Style

As a guideline, AP style only suggest using Roman numerals for:

• Wars (e.g., Word War I, World War II).
• Sequential titles of monarchs (e.g., Queen Elizabeth II).
• Certain legislative acts (e.g., Title IX).

Otherwise, the AP Stylebook suggests using Roman numerals sparingly.

Numbers in Headlines

AP style recommends using numerals for numbers in headlines. This applies even for numbers under ten and when a number appears at the start of a headline.

The only exceptions to this rule are the following:

1. Casual usages (e.g., “One of the first…” and “Hundreds of people…,” not “1 of the first…” or “100s of people…”)
2. Numbers in proper names that are conventionally written as words (e.g., “Six Flags announces…,” not “6 Flags announces…”)

Keep an eye out for these exceptions if you’re using numbers in a title or headline.

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